Abstract Ambient sunlight-driven CO 2 methanation cannot be realized due to the temperature being less than 80 °C upon irradiation with dispersed solar energy. In this work, a selective light absorber was used to construct a photothermal system to generate a high temperature (up to 288 °C) under weak solar irradiation (1 kW m −2 ), and this temperature is three times higher than that in traditional photothermal catalysis systems. Moreover, ultrathin amorphous Y 2 O 3 nanosheets with confined single nickel atoms (SA Ni/Y 2 O 3 ) were synthesized, and they exhibited superior CO 2 methanation activity. As a result, 80% CO 2 conversion efficiency and a CH 4 production rate of 7.5 L m −2 h −1 were achieved through SA Ni/Y 2 O 3 under solar irradiation (from 0.52 to 0.7 kW m −2 ) when assisted by a selective light absorber, demonstrating that this system can serve as a platform for directly harnessing dispersed solar energy to convert CO 2 to valuable chemicals.